Incandescent-cathode arc device.



C. V. FERGUSON.

INCANDESOENT CATHODE ARC DEVICE.

APPLICATION man SEPT. 90. ms.

1,267,199. Patented May 21,1918.

Fig. I.

AAAAAAAAA I""""l Inventor: Charles V. Ferguson,

His Jqttorney.

UNITED STATES PATENT OFFICE. cnmns v: motor, or scngncrnnr, mm roux,ABBIGNOB To onmn,

ELECTRIC COMPANY, A CORPORATION 01' NEW YOIK. INOANDESOEM-CATHODE ARCDEVICE,

1,267,199. ndi i m" Palm- Patented May 21, 1918. Application fliedSeptember 20, 1915. Serial No. 51,681.

To all whom it may concern: is pointed; and Fig. 3 illustrates a deviceBe it known that I, CHARLES V. FERGUSON, havin a mercury anode.

a citizen of the United States, residin at Re erring to Fig. 1 thedischarge device Schenectady, county of Schenectady, tate consists of asealed envelop 1 which consists of New York, have invented certain newand of glass, quartz or the like, and the cathode to useful Improvementsin Incandescent-Cath 2 and anode 9, both of these electrodes being odeArc Devices, of which the following is a sealed into the container inthe usual manspecification. ner and consisting of hi hly refractorysubthe spec1 c arrangement of cathode and cathode stem and connecte Thepresent invention relates to electrical stances such, for examp e, astungsten, tandischarge devices of the incandescent cathtalum, carbon andthe like. The cathode 2 ode type having a gaseous filling, and itsconsists of several parts, namely, an arcing object is to provide asimple, rugged device tip 3, connected to a stem 4 havin a (lihaving a,commercially long life ameter small enough to afford enoug resist- Myinvention is particularly applicable ance to the conduction of heat toenable the to devices having an asymmetr conductivarcing tip 3 tooperate at incandescence. ity, such, for example, as rect -s for alter-The stem 4 is connected to a current-convey nating current. ingconductor 5 sealed into a stem 6. The

hen an arc is operated in an inert atarcin ti should be so arranged andsup mosphere of gases or vapors from a cathode porte t rat the heat lostby conduction adapted to be independently heated by pas throu h thesupporting stem consists of such 76 sage of current analogous to alighting filaa sum 1 fraction of the total heat developed ment thestartin of the arc can be convenby the cathode that the arcing tip ismain iently accomplis ed, but this arrangement tamed at a uniformly hightemperature by possesses a limitation in the fact that elecacomparatively small amount of ener trical disintegration may cause thefilament Consequently with a given current the total 80 to wear awaylocally and break. voltage across the arc is lower than it would Inaccordance with one embodiment of be if: no section of reduced diameterwere my invention, I have provided a discharge provided. This result canbe conveniently device having a cathode comprising a rugobtained byreducing the diameter of a god electrode, adapted to be heated onlysmall section 7 of the supporting stem adby passage of current throughthe gas, such, 3o1n1ng the arcing tip as shown in Figs. 2 for example,as a rod having a tip which is and 3. In some cases the cathode has aproportioned to operate at incandescence, to- P inted or sharpened tip,as shown in Figs. gether with means for initially starting an 2 and 3 t0facilltate starting and secure are between the electrodes of the devicegrea er stability of the arc. whereby the cathode will be heated to in-N r he arcing ti of the cathode is procandescence. The incandescent tipmay be vided the Starting lament 8 consisting of made large enou h tomake electrical erorefractory material such as tungsten, tansion negli'ble. Iy invention also includes talum or carbon spirally spacedabout.the

to the cathode starting filament, the latter being electrically stem 4at one end near the tip 3 as indicated, connected to the cathode and inclose 'therthe end remote from the arcing tip of the ma] relationthereto while being located at a cathode being attached to a separatelead 5 greater distance from the anode than the sealed into the stem 6of the device in the arcing tip of the cathode so as to avoid havusualmanner. By this construction the ing t e arc emanate from the filamentinstartln filament is located a greater disstead of from the arcing tipof the cathode. tance rom the anode 9 than the arcing tip In theaccompanying drawin Figure 1 of the cathode in order to guard againstthe illustrates diagrammatically a d ischarge dearc deserting the ti 3and running to the vice suitable for rectifying alternating curstartingfilament eit er entirely or 1n part. rent and provided with a startingfilament; The anode 9 may have any convenient Fig. 2 illustrates amodification in which shape and may consist of refracto material thestartin filament is omitted and the are such as tungsten or carbon or voatilizable is started )y means of a high volta e dismaterial, such asmercury, as shown at 10 charge from the cathode which pre erably in Fig.3. In a rectifier the anode should have a materially greater heatdissipating capacity than the cathode to enable it to remain below atemperature of about 700 C. at the normal operating current of thedevice.

In the preparation of the device the space within the envelop should becarefull exhausted of all gases and vapors, cure ing taken to removeelectro-negative gases, such as oxygen or chlorin, or substancesyielding electro-negative gases, for example, water vapor. A trace ofoxygen does little harm when the electrodes consist of oxidizable metal,such as tungsten or 11101 bdenum as the oxygen combines chemicalwith'the heated electrodes to form non-v0 atile oxids. The envelop isfilled with a gas inert t0 the electrodes, as, for example, argon,nitrogen, crypton, neon, hydrogen, at a pressure which may be betweenseveral millimeters and atmospheric pressure or more. These gases shouldbe substantially free from electronegative gaseous impurities. For lowvoltage rectifier-s a gaseous pressure of 5 to 12 millimeters of mercuryis desirable but no definite limit of gas pressure can be given as itwill in general vary with the voltage upon which the device is operatedand the character of the service required of the device. In some casesthe gaseous filling ma be constituted by the vapor of a materiaordinarily a liquid, for example, mercury. The envelop should be propery proportioned with respect to the energy consumed during the operationof the device to dissipate heat at a rate which will result in anoperating temperature at which the vaporizable material as the desiredvapor pressure.

The arc is started by heating the filament 8 to incandescence bysuitable current introduced through the leads 5, 5 by the conductors 11,12, from any convenient source, such, for example, as the secondary 13of a transformer 14. When the filament has been heated to incandescence,a current of suitable voltage is impressed between cathode and anode. Asshown in the drawing the device may be used to rectify alternatingcurrent supplied from the transformer secondar winding 15 throughconductors 16, 17. he are initially runs from the incandescent filament8 to the anode and serves to heat the starting tip 3 to incandescenceboth by heat conduction from the filament which is connected to the tipand by reason of the roximit of the ti of the are as well as the eatedfi ament. he circuit of the starting filament me then be opened by aswitch 18. The are w' I continue to operate from the incandescent tip 3to waves of current being conducted by the device illustrated. Therectified current may be used for any desired purpose such, for example,as charging the storage battery 19. As the arcing tip 3 has a.relatively greater the anode, only half mass than the filamentelectrical erosion or disintegration will have but very littledeleterious effect. The filament 8 is used only for a very short timewhen the device 18 started, hence the electrical disintegration of thefilament is no ligible. For these reasons the device wifi have acommercially long life.

1n some cases, as shown in Fig. 2, the starting filament may be entirelydispensed w1th when the device is to be used only for relatively highvoltages. In that case the arcing tip 3 is made shar or pointed to suchan extent that the arc wi 1 be certain to start from the point of theelectrode as cathode whena re atively high volta e is applied to theterminals of the device, or example, as by means of an auxiliarytransformer winding 20. After the mam cathode has been heated toincandescence the switch 21 ma be again opened and the switch 22 closed.have found that by thus using a pointed electrode an arc may be startedat a potential of about 60% as great as the voltage required to startwith a large surface as cathode. In other respects the device shown inFig. 2 is the same as that already described in connection with Fig. 1.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,

1. A refractory cathode for an electric arc device comprising asupporting stem, an arcing tip therefor of greater diameter than saidstem, and a refracto conductor connected to said stem near said arcingtip and extending away from said tip.

2. A rectifier comprising a sealed container a filling of inert gastherein, a cathode, the tip of said cathode being proportioned tooperate at incandescence and having electrical connections at oneterminal only, a co'operating anode and means constituting part of saidcathode for assisting the starting of an arc in said device whereby theti of said cathode will be heated to incan escence.

3. An electrical arc device comprising a sealed container, a filling ofgas therein having at the operating temperature of the device a vaporpressure materially in excess of several millimeters of mercur a cathodecomprising a rod-shaped con actor of. refractory metal, comprising astem and a tip of greater diameter to permit electrical erosion withoutdeleterious efiect, a codperating anode having a materially greaterheat-dissipating capacity than the cathode,

and means constitutin part of said cathode for assisting the starting ofan arcin said device.

4. A rectifier comprising a' sealed container, a filling of inert gastherein, a refractory sharp-pointed cat ode proportioned to operate atmcandescence, comprising a supporting stem and an arcing tip of greatermass than said stem to permit electrical erosion without deleteriouseifect, and a cooperating anode of lar r mass than the cathode, saidelectrodes eing proportioned to enable an arc to start from cathode toanode at a materially lower voltage than in a reverse direction.

5. An electrical are device comprising a sealed container, a filling ofgas therein, a. cathode, the tip of which is proportioned to operate atincandescence and having an electrical connection at one end only, ananode, a refracto conductor electrically connected at one en to thecathode near the arcin tip and extending away from the anode, andconnections for conducting current to said electrode.

6. An electrical are device comprising a. sealed container, a filling ofinert gas therein at a pressure exceeding several millimeters ofmercury, a cathode, the tip of which is proportioned to operate atincandescence and is electricall connected at one end only, an anode, are ractory auxiliary electrode electrically connected at one end to thecathode near the arcing tip, extendin away from the anode, and spirallyspace about the cathode, and electrical connections for conductingcurrent through said auxiliary electrode.

In witness whereof, I have hereunto set my hand this 17th day ofSeptember, 1915.

CHARLES V. FERGUSON.

